Electric switch with improved cam operated pivoted contact

ABSTRACT

A switch particularly adapted for use with a variable resistance mechanism comprises a first fixed contact having an arcuate contact edge, a second generally U-shaped fixed contact spaced from said first fixed contact, and a resilient movable contact, one end of which is secured to one leg of the second fixed contact, said movable contact being normally flexed with its other free end biased into engagement with the arcuate edge of said first fixed contact. A rotor is provided with an integrally formed projection having a recess adapted to engage the free end of said movable contact in confining relationship. Electrical connection between the first and second fixed contacts through the movable contact is broken as the rotor is rotated in one direction engaging the free end of the movable contact in the recess formed in said projection. The rotation of the rotor in the opposite direction allows the movable contact to resile into operative electrical engagement with said first fixed contact. This is accomplished by means of a stop member on the other leg of said second fixed contact adapted to engage the free end of said movable contact.

United States Patent Tsumoru [21] Appl. No.: 79,032

[30] Foreign Application Priority Data Oct. 14, 1969 Japan ..44/98006[52] 11.8. CI ..200/6 BB, 200/ l 1 R, 200/166 8H [51] Int. Cl ..H0lh1/06, HOlh 1/34 [58] Field of Search ..200/5 R, 11 R, 6 BB, 16 R,

200/166 Bl-l; 338/200 [5 6] References Cited UNITED STATES PATENTS3,324,261 6/1967 Burns ..200/166 BH X- 2,939,337 6/1960 Sweger... ZOO/6BB X 2,942,221 6/1960 Girolamo ..338/200 2,870,273 1/1959 Merchant...200/l6 R X 3,221,115 11/1965 Feher ..200/16 R [451 June 6,1972

3,497,643 2/1970 Heath ..200/6 BB Primary Examiner.l. R. ScottAttorneylames and Franklin [57] ABSTRACT A switch particularly adaptedfor use with a variable resistance mechanism comprises a first fixedcontact having an arcuate contact edge, a second generally U-shapedfixed contact spaced from said first fixed contact, and a resilientmovable contact, one end of which is secured to one leg of the secondfixed contact, said movable contact being normally flexed with its otherfree end biased into engagement with the arcuate edge of said firstfixed contact. A rotor is provided with an integrally formed projectionhaving a recess adapted to engage the free end of said movable contactin confining relationship. Electrical connection between the first andsecond fixed contacts through the movable contact is broken as the rotoris rotated in onedirection engaging the free end of the movable contactin the recess formed in said projection. The rotation of the rotor inthe opposite direction allows the movable contact to resile intooperative electrical engagement with said first fixed contact. This isaccomplished by means of a stop member on the other leg of said secondfixed contact adapted to engage the free end of said movable contact.

21 Claims, 8 Drawing Figures PATENTEnJun 6 I972 SHEET 10F 2 FIG. 2A

i Jr my n B 2 INVENTOR rsu/va/au 0K4 ATTORNEY PATENTEDJun 6 m2 SHEET 2OF 2 /2 Ya 7a FIG. 3 21 x INVENTOR TSuMOIEU OKA ATTORNEY ELECTRIC SWITCHWITH IMPROVED CAM OPERATED PIVOTED CONTACT This invention relates to anelectrical contact switch and more particularly to a switch adapted foruse with a variable resistor or rheostat mechanism.

Electrical switches of the type herein described are designed to makeand break electrical contact between two fixed contact members inresponse to the rotation'of a rotor. The same rotor is adapted tocontrol the resistance of a rheostat or potentiometer mechanism whichmay be connected in the same circuit.

In prior art electrical switches of this type, it has been necessary toprovide a switch of considerable size with a large switching angle toeffect the necessary switching operation. The use of such largeswitching angles considerably limits the angle of rotation of the rotorwhich is effective to vary the resistance of the rheostat mechanism. Inaddition electrical contact switches of this type are susceptible todeposits of dirt and grime and oxidation of the operative contactsurfaces, thereby interfering with the establishment of good electricalcontact. Finally, over a period of time wear or deformation of theoperative contact elements may have a deleterious effect on the makingand breaking of the electrical contact. Accordingly it is a primaryobject of the present invention to provide a miniature electricalcontact switch adapted for use with a rheostat or the like in which theoperative switching angle is relatively small.

It is a further object of the present invention to provide an electricalcontact switch in which the operative contact elements are adapted toprovide a self-cleaning operation on the contact surfaces duringoperation.

It is yet another object of the present invention to design anelectrical contact switch in which the on and off conditions arepositively effected and maintained notwithstanding considerable wearand/or pennanent deformation of the operative contact elements.

To these ends the present invention resides in a switch comprising arotor formed with a projection having a recess therein, two fixedcontacts, and an elongated resilient movable contact secured at one endto one of said fixed contacts, its other end being free and normallybiased into operative electrical engagement with the other fixed contactby virtue of its resiliency. Rotation of the rotor in a first directionis effective to break electrical contact between the free end of theresilient member and the other fixed contact, the recess in saidprojection moving into confining engagement with said free end of saidmovable contact. Means are provided for releasing the free end of themovable contact from its engagement with the recess on said projectionas the rotor is rotated in the opposite direction.

To the accomplishment of the above, and to such other objects as mayhereinafter appear, thepresent invention relates to an electricalcontact switch as defined in the appended claims and as described hereinwith reference to the accompanying drawings in which:

FIG. I is an exploded perspective view of a switch in accordance withthe present invention in association with a variable resistor mechanism;

FIG. 2A is a front elevational view of the assembled switch and variableresistor of FIG. 1;

FIG. 2B is a side elevational and variable resistor of FIG. 1;

FIGS. 3A through 30 are schematic illustrations showing in successivesteps the operation of the switch in breaking electrical contact;

FIG. 3D is a schematic illustration showing the method ofre-establishing electrical contact; and

FIG. 4 is a schematic illustration of the two fixed contacts showingpossible modifications in the shape thereof.

Referring now to the drawingsand specifically to FIGS. 1 and 2A theswitching mechanism of the present invention comprises a flat circularswitch base 2 of insulating material adapted to mount the operativeswitching elements. For this view of the assembled switch purpose it isprovided with two narrow slots 4 and 5 and is notched at 6 at fourevenly spaced points along its periphery.

through corresponding slot 4 in switch base 2 and to be electricallyconnected to appropriate leads in the circuit. A second fixed contact 16comprises a generally U-shaped contact member 18 having two leg portions20 and 22 respectively extending horizontally in parallel relationship.The smaller leg 20 is provided at its inner edge near its free end witha groove or cut out portion 24 adapted to receive one end of a resilientcontact as will hereinafter be described. Fixed contact 16 is likewiseprovided with a vertically extending terminal 26 adapted to be insertedthrough corresponding slot 5 in switch base 2 and to be electricallyconnected to appropriate leads in the circuit.

The resilient contact is generally designated 28 and comprises a stripof resilient metal provided with a slot 30 at one end thereof adapted toengage the cut out portion 24 in leg 20 of fixed contact 16. The otherend 32 of movable contact 28 is bent over in a generally U-shapedconfiguration and constitutes the free movable contact surface thereof.Resilient contact 28 is shown in FIG. 1 in its unstressed or unflexedposition in which it will be noted that its ends 30 and 32 are cally inFIG. 3A movable contact 28 is fixedly secured to fixed contact 16 by themating of slot 30 and cut out portion 24. For proper electrical contactit may be necessary to apply solder at this connection. Referring againto FIG. 1 a cylindrical metallic cover member generally designated 34 isadapted to house the movable contact 28 and the two fixed contacts 8 and16 in the proper operative relationship. For this purpose member 34 isprovided with four vertically extending tabs 36 equally spaced along theperiphery of its upper surface and adapted to register with peripheralnotches 6 on switch base 2. Accordingly, the switch is assembled bysecuring movable contact 28 to fixed contact 16 as previously describedand inserting terminals 14 and 26 through slots 4 and 5, respectively,of switch base 2. Cover member 34 is then inserted over the entireassembly with tabs 36 extending through notches 6. As best shown in FIG.2A the tabs 36 are bent over onto the base member 2 to secure the switchassembly in place.

Referring again to FIG. 3A it will be seen that in the assembledconfiguration the resiliency of movable contact 28 is effective to urgeits free end 32 forcefully into engagement with the arcuate contactsurface 12 of the other fixed contact 8. This constitutes the closedposition of the switch.

The foregoing switch assembly is adapted for use with a rotatablyadjustable variable resistor or rheostat mechanism. One such mechanismgenerally designated 38 is illustrated in exploded perspective in theposes, the switch assembly being adapted for use with a variety ofmechanisms of this general type. As shown the rheostat assemblycomprises a rotor body generally designated 40, a resist'or bodygenerally designated 42 and a control shaft 44.

Resistor body 42 comprises a base 46 having a central aperture 48 and ahollow tubular member 50 extending downwardly therefrom and cooperatingwith aperture 48 to define a passage through which control shaft 44extends. Disposed on the upper surface of base 46 is a generally Ushaped resistor 52 defining an outer track and an inner conductive track53 spaced from resistor track 52. The body 42 is provided with threevertically extending terminals 54, 56 and 58, respectively. The outerterminals 54 and 58 are electrically connected to the two legsrespectively of the resistor track 52 and the middle terminal 56 iselectrically connected to the conductive track 53 in any suitablemanner.

I Control shaft 44 is provided with a portion 60 of reduced crosssection which carries a nutlike portion 62 at its terminal nutlike body62 on control shaft 44. Nutlike body 62 is adapted to extend throughcorresponding aperture 68 thus placing rotor 40 in driving relationshipwith control shaft 44. Rotor 40 is provided with two brushes 70 and 72extending therefrom and adapted to ride on resistive track 52 andconductive track 53 respectively as the rotor is driven by means ofcontrol shaft 44. In practice terminals 54 and 58 are connected across avoltage source. Terminal 56 constitutes the pick-off terminal and itspotential will vary between that of terminals 54 and 58 depending uponthe position of brush 70 on resistive track 52 which in turn will dependupon the rotative position of control shaft 44.

Rotor body 66 is provided at its upper surface with an integrally formedvertically extending projection 74 having a generally V-shaped recess 76adapted to engage the free end 32 of resilient contact 28. As bestillustrated in FIG. 3A the rheostat mechanism 38 is assembledinoperative position adjacent the switch assembly with projection 74extending into the plane of rotation of movable contact 28. Cover member34 is provided with a second set of four equally spaced tabs 78extending from its lower surface and adapted to engage fourcorresponding notches 80 in the periphery of resistor base 46 in thesame manner previously described with respect to tabs 36.

The operation of the device will now be explained with reference toFIGS. 3A through 3D. As previously mentioned FIG. 3A schematicallyillustrates the closed or on position of the movable contact 28 with itsfree end 32 resiliently pressed against contact surface 12 of fixedcontact 8. Projection 74 of rotor 40 is shown spaced from movablecontact 28 somewhat to the right thereof. Referring now to FIG. 38, asthe rotor is rotated counterclockwise (in the direction of arrow 82) bymeans of control shaft 44 projection 74 engages free end 32 of movablecontact 28 causing the elastic deformation shown in FIG. 3B. Continuedcounterclockwise rotation of projection 74 will force free end 32 ofcontact 28 into recess 76 as shown in FIG. 3C. In this position theswitch is open, the free end 32 of contact 28 being substantially spacedfrom contact surface 12 of fixed contact 8 by virtue of its snugengagement within the recess 76 of projection 74. Referring now to FIG.3D, as rotor 40 and thus projection 74 is rotated clockwise (in thedirection of arrow 84) by means of control shaft 44 the free end 32 ofmovable contact 28 remains confined in recess 76 and travels therewithremaining out of engagement with fixed contact 8 until it reaches theposition shown in FIG. 3D. At this point it will be noted that end'32 ofcontact 28 engages the inclined surface 88 of leg 22 of U- shapedcontact 18 and thus further movement of projection 74 will result in thedisengagement of free end 32 from recess 76. As a result contact 28 willresile or snap back into the posi tion shown in FIG. 3A to again closethe circuit.

In operation tenninals 14 and 26 will normally be connected in the samecircuit as terminal 56 on resistor body 42.

- Thus it will be possible by turning a single control shaft to switchon power in the circuit and adjust the desired potential. The range ofresistance variation and thus the range of voltages to which terminal 56may be subjected will depend upon that portion of the turning radius ofcontrol shaft 44 which is taken up in the switching action. Thus inorder to increase the resistance range it is necessary to decrease theswitching angle required to move resilient contact 28 from the positionshown in FIG. SC to that position in FIG. 3D.

As best illustrated in FIG. 4 the switching angle may be considerablyreduced by modifying the configuration of the contact surface 12 offixed contact 8 and/or the configuration of the leg 22 of fixed contact16 defining the stop member. Two such modifications of contact surface12 are there shown in dotted lines and dot-dash lines, respectively. Inthis manner the initial off position of projection 74 (FIG. 3C) will bemoved somewhat to the right. In addition, leg 22 may be moved to theleft to shorten the counterclockwise stroke of movable contact 28 whenengaged in recess 76.

It will be apparent from the foregoing that I have provided a switchwhich is relatively simple in construction and operation and is adaptedto make and break a circuit under the control of the rotor of a variableresistance mechanism.

A relatively small switching angle is provided by an appropriate designof the shape of the fixed contacts. Moreover, since the movable contactslides with considerable pressure on the contact surface 12 of fixedcontact 8 during switching, there is a self-cleaning effect associatedtherewith to maintain the contact surfaces free of dirt, grime or otherforeign matter.

Finally because contact surface 12 is curved, wear of the contactmembers and/or permanent deformation of resilient contact 28 will notadversely affect the making or breaking of electrical contact but ratherwill merely result in the free end 32 of resilient contact 28 engaging adifferent portion of contact surface 12.

While only one preferred embodiment of the present invention has beenspecifically described herein, it will be appreciated that manyvariations may be made therein, all within the scope of the presentinvention as defined in the following claims.

I claim:

1. An electrical contact switch comprising a frame, a contact fixedlymounted on said frame, a movable contact mounted onsaid frame so as tobe normally biased in a given direction against the fixed contact tooperatively electrically connect said contacts, and a movable membermounted on said frame movable in a first direction having a substantialcomponent of movement transverse to said given direction and in a seconddirection and effective on movement thereof in said first direction toholdingly engage said movable contact and carry it generally in saidfirst direction and out of operative engagement with said fixedcontact,and means to release said movable contact from said movable member uponmove ment of said movable member in said second direction, therebyallowing said movable contact toreturn to its normally biased positionin engagement with said fixed contact.

2. The switch of claim 1, wherein said movable member is provided with arecess adapted to holdingly receive an end of said movable contactthereby to move said received end of said movable contact out ofengagement with said fixed contact on movement of said movable member insaid first direction.

3. The switch of claim 1, wherein said fixed contact is provided with acurved contact surface. I

4. The switch of claim 2, wherein said fixed contact is provided with acurved contact surface.

5. The switch of claim 2, wherein said movable contact is resilient andis normally biased by its resilience against said fixed contact andwherein said release means is effective to release said received end ofsaid movable contact from its engagement with said recess, thereby toallow said received end of said movable contact to resile intoengagement with said fixed contact.

6. The switch of claim 2, wherein said releasing means comprises stopmeans mounted on said frame adjacent the path of movement of saidmovable member in said second direction and effective to engage saidother end of said movable contact, thereby to disengage said other endof said movable contact from said recess as said movable member moves insaid second direction past said stop means.

7. The switch of claim 1, wherein said movable member is operativelyconnected to the rotor of a variable resistance mechanism.

8. The switch of claim 1, wherein said releasing means comprises stopmeans mounted on said frame adjacent the path of movement of saidmovable member in said second direction and effective to engage saidmovable contact as the latter is holdingly carried by said movablemember as the latter moves in said second direction and then disengagesaid movable contact from said movable member as said movable membermoves past said stop means.

9. An electrical contact switch comprising a frame, first and secondcontacts fixedly mounted on said frame, a movable contact secured at oneend to one of said fixed contacts, its other end being normally biasedin a given direction against the other of said fixed contacts tooperatively electrically connect said fixed contacts, and a movablemember mounted on said frame movable therein in a first direction and ina second direction and effective on movement thereof in said firstdirection to holdingly engage said other end of said movable contact andcarry it generally in said first direction and out of operativeengagement with said other fixed contact, and means to release saidmovable contact from said movable member upon movement of said movablemember in said second direction thereby allowing said movable contact toreturn to its normally biased position, said releasing means comprisingstop means on said one fixed contact effective to engage said other endof said movable contact thereby to disengage said other end of saidmovable contact from said recess as said movable member moves in saidsecond direction past said stop means.

10. The switch of claim 9, wherein said other fixed contact is providedwith a curved contact surface.

11. The switch of claim 9, wherein said other fixed contact is providedwith a curved contact surface.

12. The switch of-claim 9, wherein said movable contact is resilient andis normally biased by its resilience against said other fixed contactand wherein said release means is effective to release said other end ofsaid movable contact from its engagement with said recess, thereby toallow said other end of said movable contact to resile into engagementwith said other fixed contact.

13. The switch of claim 9, wherein said operatively connected to therotor mechanism.

14. An electrical contact switch comprising a frame, a contact fixedlymounted on said frame and having an engageable contact surface, amovable contact mounted on said frame so as to be normally biased in agiven direction against said engageable surface of said fixed contact tooperatively electrically connect said contacts, and a movable membermounted on said frame and movable in a first direction and in a seconddirection and effective on movement thereof in said first direction toholdingly engage said movable contact and carry it generally in saidfirst direction and also impart a degree of movement thereto in adirection different from said first direction generally opposite to saidgiven direction, thereby to move said movable contact out of operativeengagement with said fixed contact, and means to release said movablecontact from said movable member upon movement of said movable member insaid second direction, thereby allowing said movable contact to returnto its normally biased position in engagement with said fixed contact.

15. The switch of claim 14, wherein said movable member is provided witha recess adapted to holdingly receive an end of said movable contactthereby to move said received end of movable member is of a variableresistance said second direction past 17. The switch of claim 14,wherein said releasing means mounted on said frame adjacent the saidmovable member in said second direction and effective to engage saidmovable contact as the latter is holdingly carried lay said movablemember as the latter moves in said second irection and then disengagesaid movable contact from said movable member as said movable membermoves past said stop means.

18. An electrical contact switch comprising a frame, a conit generallyin said first direction and out of operative engagement with said fixedcontact against said bias, and effective upon a first increment ofmovement thereof in said second direction to holdingly engage saidmovable contact and carry it generally in said second direction awayfrom said fixed contact against said bias, and means to release saidmovable contact from said movable member upon a second increment ofmovable member in said second direction, subsequent to said firstincrement thereof, thereby allowing said movable contact to return toits normally biased position in engagement with said fixed contact.

19. The switch of claim 18, wherein said movable member is provided witha recess adapted to holdingly receive an end of said movable contactthereby to move said received end of said movable contact out ofengagement with said fixed contact on movement of said movable member insaid first direction.

20. The switch of claim 19, wherein said releasing means comprises stopmeans mounted on said frame adjacent the direction and effective toengage said other end of said movable contact, thereby to disengage saidother end of said movable contact from said recess as said movablemember moves in said second direction past said stop means.

21. The switch of claim 18, wherein said releasing means comprises stopmeans mounted on said frame adjacent the path of movement of saidmovable member in said second direction and effective to engage saidmovable contact as the latter is holdingly carried by said movablemember as the latter moves in said second direction and then disengagesaid movable contact from said movable member as said movable membermoves past said stop means.

- UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent; No.3,668,345 Dated June 6, 1972 Inven tofls) Tsumoru Oka It is certifiedthat error appears iri the above-identified patent and that said LettersPatent are hereby corrected as shown below:

On the cover sheet [72] the inventor's name "Oka Tsumoru" should readTsumoru Oka,

Signed and sealed this 7th day of November 1972.

(SEAL) Attest:

EDWARD M .FLETCHER, JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents ORM PO-1050 (10-69) uscoMM-Dc 60376-P69 U.S GOVERNMENTPRINTING OFFICE: I969 0-366-334,

- UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,668,345 I I D te June 6, 1212 lnvenfofls) Tsumoru Oka It is certifiedthat error'appeai's in the above-identifiedpatent and that said LettersPatent are hereby corrected as shown below:

On the cover sheet [72] the inventor's name "Oka Tsumoru" should readTsumoru Oka Signed and sealed this 7th day of November 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. Attesting' Officer ROBERT GGTTSCHALK Commissionerof Patents FORM 304050 (10-69) USCOMM-DC 603764 69 a U.S. GOVERNMENTPRNYING OFFICE I 969 036B"334.

1. An electrical contact switch comprising a frame, a contact fixedlymounted on said frame, a movablE contact mounted on said frame so as tobe normally biased in a given direction against the fixed contact tooperatively electrically connect said contacts, and a movable membermounted on said frame movable in a first direction having a substantialcomponent of movement transverse to said given direction and in a seconddirection and effective on movement thereof in said first direction toholdingly engage said movable contact and carry it generally in saidfirst direction and out of operative engagement with said fixed contact,and means to release said movable contact from said movable member uponmovement of said movable member in said second direction, therebyallowing said movable contact to return to its normally biased positionin engagement with said fixed contact.
 2. The switch of claim 1, whereinsaid movable member is provided with a recess adapted to holdinglyreceive an end of said movable contact thereby to move said received endof said movable contact out of engagement with said fixed contact onmovement of said movable member in said first direction.
 3. The switchof claim 1, wherein said fixed contact is provided with a curved contactsurface.
 4. The switch of claim 2, wherein said fixed contact isprovided with a curved contact surface.
 5. The switch of claim 2,wherein said movable contact is resilient and is normally biased by itsresilience against said fixed contact and wherein said release means iseffective to release said received end of said movable contact from itsengagement with said recess, thereby to allow said received end of saidmovable contact to resile into engagement with said fixed contact. 6.The switch of claim 2, wherein said releasing means comprises stop meansmounted on said frame adjacent the path of movement of said movablemember in said second direction and effective to engage said other endof said movable contact, thereby to disengage said other end of saidmovable contact from said recess as said movable member moves in saidsecond direction past said stop means.
 7. The switch of claim 1, whereinsaid movable member is operatively connected to the rotor of a variableresistance mechanism.
 8. The switch of claim 1, wherein said releasingmeans comprises stop means mounted on said frame adjacent the path ofmovement of said movable member in said second direction and effectiveto engage said movable contact as the latter is holdingly carried bysaid movable member as the latter moves in said second direction andthen disengage said movable contact from said movable member as saidmovable member moves past said stop means.
 9. An electrical contactswitch comprising a frame, first and second contacts fixedly mounted onsaid frame, a movable contact secured at one end to one of said fixedcontacts, its other end being normally biased in a given directionagainst the other of said fixed contacts to operatively electricallyconnect said fixed contacts, and a movable member mounted on said framemovable therein in a first direction and in a second direction andeffective on movement thereof in said first direction to holdinglyengage said other end of said movable contact and carry it generally insaid first direction and out of operative engagement with said otherfixed contact, and means to release said movable contact from saidmovable member upon movement of said movable member in said seconddirection thereby allowing said movable contact to return to itsnormally biased position, said releasing means comprising stop means onsaid one fixed contact effective to engage said other end of saidmovable contact thereby to disengage said other end of said movablecontact from said recess as said movable member moves in said seconddirection past said stop means.
 10. The switch of claim 9, wherein saidother fixed contact is provided with a curved contact surface.
 11. Theswitch of claim 9, wherein said other fixed contact is provided with acurved contact surface.
 12. The switch of claim 9, wherein said mOvablecontact is resilient and is normally biased by its resilience againstsaid other fixed contact and wherein said release means is effective torelease said other end of said movable contact from its engagement withsaid recess, thereby to allow said other end of said movable contact toresile into engagement with said other fixed contact.
 13. The switch ofclaim 9, wherein said movable member is operatively connected to therotor of a variable resistance mechanism.
 14. An electrical contactswitch comprising a frame, a contact fixedly mounted on said frame andhaving an engageable contact surface, a movable contact mounted on saidframe so as to be normally biased in a given direction against saidengageable surface of said fixed contact to operatively electricallyconnect said contacts, and a movable member mounted on said frame andmovable in a first direction and in a second direction and effective onmovement thereof in said first direction to holdingly engage saidmovable contact and carry it generally in said first direction and alsoimpart a degree of movement thereto in a direction different from saidfirst direction generally opposite to said given direction, thereby tomove said movable contact out of operative engagement with said fixedcontact, and means to release said movable contact from said movablemember upon movement of said movable member in said second direction,thereby allowing said movable contact to return to its normally biasedposition in engagement with said fixed contact.
 15. The switch of claim14, wherein said movable member is provided with a recess adapted toholdingly receive an end of said movable contact thereby to move saidreceived end of said movable contact out of engagement with said fixedcontact on movement of said movable member in said first direction. 16.The switch of claim 15, wherein said releasing means comprises stopmeans mounted on said frame adjacent the path of movement of saidmovable member in said second direction and effective to engage saidother end of said movable contact, thereby to disengage said other endof said movable contact from said recess as said movable member moves insaid second direction past said stop means.
 17. The switch of claim 14,wherein said releasing means comprises stop means mounted on said frameadjacent the path of movement of said movable member in said seconddirection and effective to engage said movable contact as the latter isholdingly carried by said movable member as the latter moves in saidsecond direction and then disengage said movable contact from saidmovable member as said movable member moves past said stop means.
 18. Anelectrical contact switch comprising a frame, a contact fixedly mountedon said frame, a movable contact mounted on said frame so as to benormally biased in a given direction against said fixed contact tooperatively electrically connect said contacts, and a movable membermounted on said frame and movable in a first direction and in a seconddirection and effective on movement thereof in said first direction toholdingly engage said movable contact and carry it generally in saidfirst direction and out of operative engagement with said fixed contactagainst said bias, and effective upon a first increment of movementthereof in said second direction to holdingly engage said movablecontact and carry it generally in said second direction away from saidfixed contact against said bias, and means to release said movablecontact from said movable member upon a second increment of movement ofsaid movable member in said second direction, subsequent to said firstincrement thereof, thereby allowing said movable contact to return toits normally biased position in engagement with said fixed contact. 19.The switch of claim 18, wherein said movable member is provided with arecess adapted to holdingly receive an end of said movable contactthereby to move said received end of said movable contact out ofengagement with said fixed contact on mOvement of said movable member insaid first direction.
 20. The switch of claim 19, wherein said releasingmeans comprises stop means mounted on said frame adjacent the path ofmovement of said movable member in said second direction and effectiveto engage said other end of said movable contact, thereby to disengagesaid other end of said movable contact from said recess as said movablemember moves in said second direction past said stop means.
 21. Theswitch of claim 18, wherein said releasing means comprises stop meansmounted on said frame adjacent the path of movement of said movablemember in said second direction and effective to engage said movablecontact as the latter is holdingly carried by said movable member as thelatter moves in said second direction and then disengage said movablecontact from said movable member as said movable member moves past saidstop means.